change colour scrollbar

Hi all, can you help me out? I have tried different kind of codes but.. nothing works. I would like to change the color of my trolling bar on the right side. it is now white and hard to see. Can you help me out?  @tuanphan would love to hear from you...,

Try this Custom CSS:

// scrollbar width
::-webkit-scrollbar {
  width: 12px; 
}
// scrollbar background
::-webkit-scrollbar-track {
  background: #ddd;
}
// scrollbar colour
::-webkit-scrollbar-thumb {
  background-color: #000;
  border-radius: 4px;
}

Change the color hex codes and width/border values.